Former Formula One boss Max Mosley won a court case after the News of the World filmed him with prostitutes. Last month he went to the European court of human rights to argue for tighter laws protecting privacy. But critics, including journalism professor Roy Greenslade, say any change would reduce press freedom. Emine Saner hears the arguments.

Roy Greenslade: I don't disagree that there was a massive invasion of your privacy. But would you not regard a person of your stature, in the job you were in, as being somebody whose private life needed to be under scrutiny?

Max Mosley: Nobody should have their private life put under scrutiny unless there is some connection between their private and public life. If you take sex, if the people are adult, consenting and it's in private, it's nobody else's business.

RG: You sued for an invasion of privacy. You had been libelled but why did you never sue for libel?

MM: I don't want to say too much about this, but by the time all the litigation is finished, what I will have done all over the world will be a lot more effective than suing for libel in Britain.

Emine Saner: Why is this so important to you?

MM: There I was, particularly when I became president of the FIA, doing all sorts of "do-gooding" things, the stuff I did for road safety, for instance. You try very hard, and you're getting to the end of [your career]. Then somebody comes along and exposes an element of your private life which you have always kept secret, which then labels you for the rest of your life and brushes aside all of the serious things you have done. Then, when you look into it, you find people whose lives have been ruined – and some have killed themselves – because their private lives were exposed. If you're an average person, if you sue, you risk losing everything. Even if you win, you lose money. I won, and even after I got the damages, it still cost £30,000. Most people can't afford to throw away £30,000, never mind £1m, which is what it would cost if they lost. What [tabloid papers] do to people is wicked. So I thought, it's time somebody did this. Fortunately, I've got the money to do it, and I was reasonably au fait with the law. How long would it be before they picked on another person? Obviously it's satisfying to stick it to the News of the World, but that's very much a side issue.

ES: What was the effect on your life?

MM: Devastating. It was totally secret, I never told my wife. We had been together for 50 years … it turned it upside down. It was worse for my sons. What gets me is that they don't give a damn about any of that if they can sell papers. This you can never recover from, and neither can your family.

RG: I hate this kind of journalism, it wasn't what I came into the job for. From the instant your case occurred, I was on your side. But now we come to your remedy: to have prior notification – make newspapers, under the law, inform people in time to allow them to take out an injunction. I believe that will be an inhibition of press freedom. There are instances where we would fail to get important stories into the public domain.

MM: If you have a couple of days' notice, it means it will come in front of a judge who is experienced [in media law].

RG: So you get a specialist judge, but the judge can't make a decision, because it isn't a full hearing in which they have all the evidence about whether something is in the public interest or not. So you have to have another hearing, probably weeks later. This immediately turns press freedom on its head. We will have our papers edited by judges, not editors. It would also cripple newspapers, especially local papers, having to go to court week after week.

MM: If the person applies [for an injunction] and doesn't get it, they pay the cost. In the same way that it might be an inhibitor for the local paper, it will also be an inhibitor for the local councillor. The only cases where papers keep a story secret are the cases where they know there will be an injunction. In most cases, there already is prior notification – apart from anything else, it makes the story more interesting. So the idea that week after week there would be applications – if that were true, that would be happening now.

RG: People don't get three days' notice. Say in the instance of the MPs' expenses, the MP, going to court because he has been notified in advance, might say, "there were genuine errors and I've sorted them out, it cannot be in the public interest to publish". You're already into a lengthy and expensive argument in court. I'm worried about the unintended consequences of a law like this – people will do all they can to use it as often as possible. You will say we're covered by public interest arguments, but cases involve grey areas. There is no definition of what the public interest is, and we have rough and ready attitudes of judges to decide and they diverge greatly. You are withholding from editors the rights to make those decisions, and giving that to judges, at a cost. Take Robert Maxwell, an example of someone who was hugely litigious and had a lot to hide. He would have been somebody who would take massive advantage of this kind of law.

ES: If Mosley is successful, how would it change the way the press operates?

RG: It would inhibit tabloid newspapers, and we wouldn't necessarily feel too bad about that. But I would be concerned that as a journalist you would be constantly looking over your shoulder, wondering at what stage do we approach this person, how much evidence do we need? Say you are mounting an investigation, and you're gathering bits and pieces. If they had this law, the subjects of this investigation could go to a judge and say, "how can the paper show this is in the public interest?" You might not have enough evidence at that stage.

MM: But that happens now – you hear something and you get your lawyer to write to the newspaper, and if they don't respond, you ask for an injunction. I'm talking about the case where nobody knows what is about to be published. You make sure that the serious investigative journalist is not inhibited, you make sure that the local newspaper can't be bullied by the wealthy councillor – those are the things you sort out once that principle is established.

RG: Let's turn this on its head. A friend of mine said, "could you not tell Max that sex is a wonderful thing, in all its manifest varieties, as I'm sure you agree. Laugh it off, get on with life, let the News of the World do what it likes. Isn't that the way to handle it?"

MM: I agree, except for one thing – people who don't want to conduct their sex lives in public shouldn't be exposed. Sex is private, unless all the participants want it to be public. If someone gets turned on by dogging, fantastic, but they haven't got a reasonable expectation of privacy [laughs]. But I don't see that anyone has the right to effectively put someone in the stocks, just because your sex life isn't to an editor's taste. That isn't consistent with modern, secular, liberal society.

• This article was amended on 10 June 2011. The original said Formula One boss Max Mosley. This has been corrected.